Method of casting

ABSTRACT

A method of casting an article includes positioning a first portion of the article, formed from a first material, in a rotatable mold. Additionally, the method includes, while rotating the mold, pouring a molten second material into the mold over the first portion to form a second portion of the article that is metallurgically bonded to the first portion of the article.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/809,029, filed Apr. 5, 2013, which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to a method of casting and,more particularly, to a method of casting articles, such as wearcomponents for compactor wheels.

BACKGROUND

Compactors such as, for example, landfill compactors and soil compactorstypically include steel wheels, which are fitted with teeth that extendradially outward from the wheels to engage and compact material overwhich the compactors are driven. Over time, the teeth wear down, andthey are replaced with newly manufactured teeth.

U.S. Pat. No. 6,632,045 to McCartney (“the '045 patent”) discloses anexemplary method of manufacturing a two-part tooth that is adapted to bewelded to a steel wheel. The tooth includes a base constructed from aweldable material, and a cap constructed of a harder metal than themetal used for the base. According to the '045 patent, the tooth ismanufactured by casting the base in a first mold, moving the base to asecond mold, and casting the cap onto the base in the second mold. Whencasting the cap, molten metal flows into mating formations of the base,ensuring that the cap is firmly keyed to the base when the molten metalsolidifies.

While the manufacturing method of the '045 patent may yield a tooth thatis appropriate for certain applications, the tooth may not bewell-suited for others. For example, the manufacturing method of the'045 patent may yield a tooth that is not well-suited for applicationsin which the tooth's weight stresses drivetrain components of acompactor without meaningfully improving compaction. In suchapplications, the tooth might cause premature failure of the drivetraincomponents, thereby unnecessarily increasing maintenance costsassociated with the compactor.

The various embodiments of the present disclosure are directed towardovercoming one or more deficiencies of the prior art.

SUMMARY

In an exemplary embodiment of the present disclosure, a method ofcasting an article includes positioning a first portion of the article,formed from a first material, in a rotatable mold. Additionally, themethod includes, while rotating the mold, pouring a molten secondmaterial into the mold over the first portion to form a second portionof the article that is metallurgically bonded to the first portion ofthe article.

In another exemplary embodiment of the present disclosure, a method ofcasting an article includes rotating a mold about an axis whileperforming several steps. The steps include pouring a molten firstmaterial into the mold to form a first portion of the article having asolid cross-section that is perpendicular to the axis. In addition, thesteps include allowing the first material to cool. The steps alsoinclude pouring a molten second material into the mold over the firstportion to form a second portion of the article that is metallurgicallybonded to the first portion of the article.

In yet another exemplary embodiment of the present disclosure, a methodof casting an article includes rotating a mold about an axis whileperforming several steps. The steps include pouring a molten firstmaterial into the mold to form a first portion of the article having across-section that is perpendicular to the axis with a non-circularouter edge. In addition, the steps include allowing the first materialto cool. The steps also include pouring a molten second material intothe mold over the first portion to form a second portion of the articlethat is metallurgically bonded to the first portion of the article.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial illustration of an exemplary wheel for use with acompactor;

FIG. 2 is a pictorial illustration of an exemplary wear component foruse with the wheel of FIG. 1;

FIG. 3 is a magnified cross-sectional view of an exemplary interfacebetween exemplary tip and base portions of the wear component of FIG. 2;

FIG. 4 is a cross-sectional view of an exemplary apparatus for castingthe wear component of FIGS. 2 and 3;

FIG. 5 is a cross-sectional view of the wear component of FIGS. 2-4 inan exemplary mold of the apparatus of FIG. 4;

FIG. 6 is a pictorial illustration of another exemplary tip portion;

FIG. 7 is a cross-sectional view of the tip portion of FIG. 6 bonded toanother exemplary base portion;

FIGS. 8-13 are pictorial illustrations of yet further exemplary tipportions; and

FIGS. 14 and 15 are flow charts describing exemplary disclosed methodsof casting articles of manufacture, such as the wear components of theother figures.

DETAILED DESCRIPTION

FIG. 1 illustrates a steel wheel 10 for use with a mobile machine, suchas a landfill or soil compactor. As shown, wear components 20 in theform of teeth are fitted to wheel 10, and extend radially outward fromwheel 10 to engage and compact material over which wheel 10 is driven.It should be understood, however, that wear components 20 may be teeththat are fitted to another type of part (e.g., a bucket) or may beanother type of wear component entirely (e.g., hammers on disk rotors ofa scrap metal shredder). In any case, in certain embodiments (e.g., theembodiment of FIG. 1), each wear component 20 may include a tip portion30 that extends radially outward from wheel 10 to engage and compactmaterial over which steel wheel 10 is driven. In these embodiments, tipportion 30 may be connected to wheel 10 by a base portion 40 of its wearcomponent 20, which may be welded to wheel 10.

Tip portion 30 may have a distal end 50 defining an exterior surface ofits wear component 20. As shown in FIG. 1, distal end 50 may begenerally I-shaped. It should be understood, however, that distal end 50may be otherwise shaped. For example, distal end 50 may be generally+(plus)-shaped. Alternatively, distal end 50 may have another shapeconducive to compacting material. Tip portion 30 may also include sidesurfaces 60 extending from distal end 50 to a proximate end 70 of tipportion 30. In certain embodiments, side surfaces 60 may be at leastpartially concave, enabling them to deflect material away from baseportion 40 and thereby protect base portion 40 from wear. Alternatively,side surfaces 60 may have other shapes that are conducive to compactingmaterial (e.g., shapes that are not at least partially concave).Regardless of tip portion 30's shape, tip portion 30 may be formed froma material with a hardness of at least 45 Rockwell C, making it highlyresistant to abrasion resulting from compaction of material. Forexample, tip portion 30 may be formed from white iron (e.g.,high-chromium white iron or Ni-Hard), carbidic iron, austempered iron,high-carbon steel, high-carbon alloy steel, tool steel, carbidic steel,or stainless steel.

Referring to FIG. 2, base portion 40 may include a mounting end 75 forattaching wear component 20 to wheel 10, a distal end 77 oppositemounting end 75, and side surfaces 78 extending from mounting end 75 todistal end 77. As shown, mounting end 75 is generally shaped to follow acontour of wheel 10, thereby facilitating the attachment of wearcomponent 20 to wheel 10. Notably, however, mounting end 75 may includea recess 80, which does not follow the contour of wheel 10. Recess 80may become a hollow cavity when wear component 20 is attached to wheel10, thereby reducing the weight of wear component 20 relative to asimilarly sized (but solid) wear component. Base portion 40 may beformed from a material with a carbon-equivalent (CE) value of less than0.7, ensuring that it can be welded to steel (e.g., steel wheel 10)using portable welding equipment in the field (as opposed to specializedwelding procedures typically required to be performed in a maintenancefacility). For example, base portion 40 may be formed from steel (e.g.,carbon steel, alloy steel, or stainless steel).

Base portion 40 may be metallurgically bonded to tip portion 30, thatis, portion 40 may be attached to portion 30 primarily by metallurgicalbonding. In particular, distal end 77 of base portion 40 may bemetallurgically bonded to proximate end 70 of tip portion 30. As shownin FIG. 3, the interface between distal end 77 and proximate end 70(“base-tip interface 100”) may thus be composed solely of a mixture ofthe material of base portion 40 and the material of tip portion 30. Thatis, base-tip interface 100 may include no adhesive or filler metal, nooxide films, and no voids.

The shape of base-tip interface 100 (and thus distal end 77 andproximate end 70) may be non-planar, and may be related to the method bywhich wear component 20 is cast. For example, referring to FIG. 4, wearcomponent 20 may be centrifugally cast using a dual-pour method in whichmolten first and second materials are poured through a funnel 120 into arotating mold 110. The molten first material may be poured first to formtip portion 30 while mold 110 is rotated at a first speed. Afterallowing the first material to cool, the second material may then bepoured over the first material (now tip portion 30) to form base portion40 while mold 110 is rotated at a second speed, which may or may not bethe same as the first speed. Both pours may take place while mold 110 isrotated about an axis 115 that is generally parallel to a direction ofgravitational acceleration (i.e., a direction in which the materialsfall as they are poured). Such rotation may cause the first material tocreep up the sides of mold 110, thereby giving proximate end 70 of tipportion 30 (and thus also base-tip interface 100) a generally paraboliccross-sectional profile, as shown in FIG. 4. It should be noted that,below base-tip interface 100, tip portion 30 may have a solid (i.e.,free of voids) cross-section that is perpendicular to axis 115, as shownin FIG. 5. Further, it should be understood that the shape of the outeredge 125 of any cross-section of tip portion 30 that is perpendicular toaxis 115 will be defined by the shape of mold 110. Thus, outer edge 125may be non-circular, as shown in FIG. 5. For example, outer edge 125 maybe generally I-shaped (as illustrated), generally +(plus)-shaped, orotherwise shaped.

In another method of centrifugally casting wear component 20, tipportion 30 may be cast, forged, or machined from a first material beforebeing positioned within mold 110. A molten second material may then bepoured into mold 110 over tip portion 30 to form base portion 40, whilemold 110 is rotated about axis 115. With this second method, proximateend 70 of tip portion 30 may begin with almost any shape. Proximate end70's shape may change slightly during molding as a result of themetallurgical bonding process, but it should be understood that theshape of base-tip interface 100 may at least generally track thebeginning shape of proximate end 70. For example, as shown in FIG. 6,proximate end 70 may begin with a plurality of recesses 130 extendingfrom a first side 140 of tip portion 30 to a second side 150 of tipportion 30. Each recess 130 may be generally valley-shaped. For example,each recess 130 may be generally U-shaped, and may be wider than it isdeep (as illustrated in FIG. 6). In certain embodiments, proximate end70 may begin with two recesses 130. Referring to FIG. 7, when the moltensecond material is poured into mold 110 over such recesses 130, thesecond material may slightly deform recesses 130 into recesses 130′. Thesecond material may then solidify to form base portion 40 with aplurality of protrusions 160, each extending into a corresponding one ofrecesses 130′ at base-tip interface 100. It should be noted that, insome embodiments, protrusions 160 and recesses 130′ may mechanicallyenhance the bond of base portion 40 to tip portion 30.

The number, shape, and placement of any protrusions 160 extending intoproximate end 70 of tip portion 30 at base-tip interface 100 may beaffected by the beginning shape of proximate end 70. For example, ratherthan beginning with recesses 130 that are wider than they are deep (asillustrated in FIG. 6), proximate end 70 may begin with recesses 130that are deeper than they are wide. As another example, rather thanbeginning with recesses 130 that are generally U-shaped (as illustratedin FIG. 6), proximate end 70 may begin with recesses 130 that aregenerally V-shaped. Alternatively, as illustrated in FIG. 8, proximateend 70 may begin with recesses 230 that are generally box-shaped. In yetanother alternative embodiment, rather than beginning with a pluralityof recesses 130 or 230 (as illustrated in FIGS. 6 and 8), proximate end70 may begin with a single recess 330, as shown in FIG. 9.

Alternatively, as illustrated in FIG. 10, proximate end 70 may beginwith a plurality of recesses 430 in the form of rabbets (i.e.,step-shaped recesses) in outer edges 435 of tip portion 30. While FIG.10 illustrates recesses 430 as extending only from first side 140 tosecond side 150, recesses 430 may also extend from a third side 440 oftip portion 30 to a fourth side 450 of tip portion 30, as shown in FIG.11.

In yet another alternative embodiment, as shown in FIGS. 12 and 13,proximate end 70 may begin with one or more recesses 530 in the form ofbathtub-shaped depressions. While such recesses 530 could be the onlyrecesses in proximate end 70, proximate end 70 could also include one ormore of the recesses discussed above. For example, as shown in FIG. 13,proximate end 70 may include two recesses 530 and four recesses 430. Infact, it should be understood that proximate end 70 may include anycombination of any number of recesses 130, 230, 330, 430, 530, and/orany other similarly shaped recesses.

FIGS. 14 and 15 are flow diagrams describing exemplary methods ofcasting articles of manufacture such as wear components 20, and theywill be discussed in the following section.

INDUSTRIAL APPLICABILITY

The disclosed wear components may be fitted to steel components and maybe particularly beneficial when fitted to steel wheels of landfill orsoil compactors. The wear components may be cast such that theyfacilitate in-field (as opposed to in-maintenance facility) maintenanceof the compactors and also minimize the amount of maintenance thecompactors require. Exemplary methods of casting articles ofmanufacture, such as the disclosed wear components, will now bedescribed.

Referring to FIG. 14, wear component 20 may be centrifugally cast usinga dual-pour method in which molten first and second materials are pouredinto mold 110 while mold 110 is rotated about axis 115 (referring toFIG. 4) (step 1400). First, a molten first material may be pouredthrough funnel 120 into mold 110 to form tip portion 30 while mold 110is rotated at a first speed (step 1410). The first material may have ahardness of at least 45 Rockwell C, making tip portion 30 highlyresistant to abrasion resulting from compaction of material and therebyreducing the number of times wear component must be replaced. Forexample, as discussed above, the first material may be white iron (e.g.,high-chromium white iron or Ni-Hard), carbidic iron, austempered iron,high-carbon steel, high-carbon alloy steel, tool steel, carbidic steel,or stainless steel. While funnel 120 may be positioned such that thefirst material is poured at a fixed location relative to axis 115 (e.g.,along axis 115), funnel 120 may alternatively be moved during thepouring such that the first material is poured at a plurality ofdifferent locations relative to axis 115. In any case, the rotation ofmold 110 may cause the first material to creep up the sides of mold 110,thereby giving proximate end 70 of tip portion 30 (and thus alsobase-tip interface 100) a generally parabolic cross-sectional profile,as shown in FIG. 4. Such a profile may enable the first material toprotect a large portion of the exterior surface of wear component 20without occupying a correspondingly large portion of the volume of wearcomponent 20, thereby minimizing the amount of the first material (whichmay be more costly than the second material) required to form wearcomponent 20.

Next, the first material may be allowed to cool (step 1420). A moltensecond material may then be poured through funnel 120, into mold 110,over the first material (now tip portion 30) to form base portion 40while mold 110 is rotated at a second speed, which may or may not be thesame as the first speed (step 1430). The second material may have acarbon-equivalent (CE) value of less than 0.7, ensuring that baseportion 40 can be welded to steel (e.g., steel wheel 10) using portablewelding equipment in the field (as opposed to specialized weldingprocedures typically required to be performed in a maintenancefacility). For example, as discussed above, the second material may becarbon steel, alloy steel, or stainless steel. While funnel 120 may bepositioned such that the second material is poured at a fixed locationrelative to axis 115 (e.g., along axis 115), funnel 120 mayalternatively be moved such that the second material is poured at aplurality of different locations relative to axis 115. Notably, therotation of mold 110 may cause the second material to move radiallyoutward along a surface of the first material when the second materialimpacts the first material, displacing any foreign materials (e.g.,oxide films) on the surface of the first material. The second materialmay then metallurgically bond base portion 40 to tip portion 30. Therotation of mold 110 may also cause the second material to creep up thesides of mold 110, facilitating the formation of recess 80 in mountingend 75 of base portion 40. This recess 80 may, in turn, become a hollowcavity when wear component 20 is attached to wheel 10, thereby reducingthe weight of wear component 20 relative to a similarly sized (butsolid) wear component. Such weight reduction may minimize stresses ondrivetrain components of compactors using wear components 20, therebyextending the life of the drivetrain components and reducing maintenancecosts associated with the drivetrain components. Additionally, theweight reduction may minimize the amount of fuel required to operate thecompactors, thereby reducing operating costs associated with thecompactors.

In alternative embodiments and referring to FIG. 15, wear component 20may be centrifugally cast using a tip portion 30 that is cast, forged,or machined from the first material before being positioned within mold110 (step 1500). In particular, tip portion 30 may be positioned withits proximate end 70 facing upward such that any material poured overtip portion 30 is poured over proximate end 70. Then, while rotatingmold 110 about axis 115 (step 1510), the molten second material may bepoured into mold 110 over tip portion 30 to form base portion 40 (step1520). Although funnel 120 may be positioned such that the secondmaterial is poured at a fixed location relative to axis 115 (e.g., alongaxis 115), funnel 120 may alternatively be moved such that the secondmaterial is poured at a plurality of different locations relative toaxis 115. Notably, the rotation of mold 110 may cause the secondmaterial to move radially outward along proximate end 70 when the secondmaterial impacts the first material, displacing any foreign materials(e.g., oxide films) on proximate end 70. In some embodiments, themovement may be at least partially guided by recesses 130, 230, 330,430, and/or 530 of proximate end 70, potentially speeding up and/orslowing down the movement, and thereby maximizing the displacement offoreign materials. The second material may then metallurgically bondbase portion 40 to tip portion 30. The rotation of mold 110 may alsocause the second material to creep up the sides of mold 110,facilitating the formation of recess 80 in the same way as discussedabove with respect to the dual-pour method.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the disclosed methodswithout departing from the scope of the disclosure. Other embodiments ofthe disclosed methods will be apparent to those skilled in the art fromconsideration of the specification and practice of the methods disclosedherein. It is intended that the specification and examples be consideredas exemplary only, with a true scope of the disclosure being indicatedby the following claims and their equivalents.

What is claimed is:
 1. A method of casting an article comprising:positioning a first portion of the article, formed from a firstmaterial, in a rotatable mold; and while rotating the mold, pouring amolten second material into the mold over the first portion to form asecond portion of the article that is metallurgically bonded to thefirst portion of the article.
 2. The method of claim 1, wherein thefirst portion of the article is precast.
 3. The method of claim 1,wherein: the first material has a hardness of at least 45 Rockwell C;and the second material has a carbon-equivalent (CE) value of less than0.7.
 4. The method of claim 3, wherein: the first material is steel oriron; and the second material is steel.
 5. The method of claim 1,wherein the pouring of the molten second material occurs while the moldis rotated about an axis generally parallel to a direction ofgravitational acceleration.
 6. The method of claim 5, wherein thepouring of the molten second material occurs at a plurality of differentlocations relative to the axis.
 7. The method of claim 1, whereinpositioning the first portion in the rotatable mold includes positioningthe first portion such that the second material is poured over an end ofthe first portion including a plurality of recesses.
 8. A method ofcasting an article comprising, while rotating a mold about an axis:pouring a molten first material into the mold to form a first portion ofthe article having a solid cross-section that is perpendicular to theaxis; allowing the first material to cool; and pouring a molten secondmaterial into the mold over the first portion to form a second portionof the article that is metallurgically bonded to the first portion ofthe article.
 9. The method of claim 8, wherein the solid cross-sectionhas a non-circular outer edge.
 10. The method of claim 9, wherein thesolid cross-section has a generally I-shaped outer edge.
 11. The methodof claim 8, wherein: the first material has a hardness of at least 45Rockwell C; and the second material has a carbon-equivalent (CE) valueof less than 0.7.
 12. The method of claim 11, wherein: the firstmaterial is steel or iron; and the second material is steel.
 13. Themethod of claim 8, wherein the axis is generally parallel to a directionof gravitational acceleration.
 14. The method of claim 8, wherein thepourings occur at a plurality of different locations relative to theaxis.
 15. A method of casting an article comprising, while rotating amold about an axis: pouring a molten first material into the mold toform a first portion of the article having a cross-section that isperpendicular to the axis with a non-circular outer edge; allowing thefirst material to cool; and pouring a molten second material into themold over the first portion to form a second portion of the article thatis metallurgically bonded to the first portion of the article.
 16. Themethod of claim 15, wherein the cross-section has a generally I-shapedouter edge.
 17. The method of claim 15, wherein: the first material hasa hardness of at least 45 Rockwell C; and the second material has acarbon-equivalent (CE) value of less than 0.7.
 18. The method of claim17, wherein: the first material is steel or iron; and the secondmaterial is steel.
 19. The method of claim 15, wherein the axis isgenerally parallel to a direction of gravitational acceleration.
 20. Themethod of claim 15, wherein the pourings occur at a plurality ofdifferent locations relative to the axis.